Method of allocating frequency subband and apparatus adopting the same

ABSTRACT

A method of allocating frequency subbands in an ultrawideband (UWB) wireless communication system and an apparatus adopting the same are provided. The method of allocating frequency subbands to a device in a communication system, the method including: (a) determining whether usage of a first frequency band including upper frequency subbands is necessary; and (b) if it is determined that the usage of the first frequency band is necessary, not setting usage permission for the first frequency band to the device and not granting access to the first frequency band if a request for usage of the first frequency band is received from the device. When generation of a new piconet is necessary or generation of a new piconet is requested in a multi-piconet environment, since subbands of a high frequency group are allocated through negotiation, frequency resources are efficiently managed.

This application claims the priority of Korean Patent Application No.2003-64586, filed on Sep. 17, 2003, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein in its entiretyby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, a method of allocating frequency subbands in anultrawideband (UWB) wireless communication system and an apparatusadopting the same.

2. Description of the Related Art

Much research has gone into finding methods utilizing a frequency bandin an ultrawideband (UWB) wireless communication system with a very widerange of frequency bandwidth. Unlike wireless data transmissiontechnology used in cellular mobile communication, satellitecommunication, and TV broadcasting in which a transmission data streamis carried on a reference frequency waveform called an RF carrier, inUWB technology, a data stream is transmitted by representing data oflogic 0 and logic 1 by repeatedly generating a plurality of pulses withequal periods and a constant waveform without using a carrier, eachpulse with a period shorter than 1 nanosecond.

That is, the UWB technology is a wireless communication technology inwhich a data stream is transmitted using a plurality of pulses playing arole similar to Morse code. For example, a data stream is transmitted bygenerating a plurality of pulses with a very short period (hundredspicoseconds) with a constant interval between each of the pulses andmodulating the pulses by adjusting periods of the pulses with a shorttime (±Dt) before and after a predetermined time so that −Dt is used fortransmitting logic 0 and +Dt is used for transmitting logic 1.Pluralities of data can be transmitted using the coded pulse signal.

FIG. 1 illustrates a network topology according to the IEEE 802.15.3standard.

A network includes a plurality of devices 101 through 104 and a piconetcoordinator (PNC) 105 which relays and manages data and commands amongthe devices 101 through 104. A piconet is a network including aplurality of devices and a PNC. The devices may be home appliances, suchas TVs and camcoders, and any of the devices can be the PNC 105.However, in general, an audio/video (AV) receiver or a computer is thePNC 105. The PNC 105 receives a channel time request command from eachof the devices 101 through 104 and allocates a channel time to each ofthe devices 101 through 104. Each of the devices 101 through 104directly transmits data to other devices at the allocated channel time.The PNC 105 also performs power save mode management and authenticationmanagement. Through the authentication management, the PNC 105distributes a key for protecting a payload, and each of the devices 101through 104 transmits and receives encrypted data using the allocatedtimeslot and the distributed key. A multi-piconet is a network includinga plurality of piconets.

FIG. 2 illustrates a distribution of a frequency band in a conventionalUWB wireless communication system.

Referring to FIG. 2, a UWB frequency band allocated from 3.1 GHz to 10.6GHz is divided into 16 subbands, each subband with a 520 MHz bandwidth.Bands 0 through 7 are defined as a low frequency group 210, a band 8 220is a reserved band reserved for a new UWB communication system such asthe ZIGBEE, and bands 9 through 15 are defined as a high frequency group230. One of the subbands in the low frequency group 210 is not used inorder to reduce interference in systems having a 5 GHz band allocatedfor a wireless LAN service as defined in the EEE 802.11a standard.Therefore, the low frequency group 210 also has 7 usable frequencysubbands.

FIG. 3 illustrates frequency hopping sequences used for the distributionof the frequency band of FIG. 2.

Referring to FIG. 3, 6 frequency hopping sequences suggested by amulti-user access method of a UWB wireless communication system thatsupports a multi-piconet in a wireless personal area network (WPAN) ofthe IEEE 802.15.3 standard are illustrated. A pulse is generated duringa dwell time such that a 7-subband sequence is not duplicated among the6 frequency hopping sequences, thus allowing 6 piconets to use the 6frequency hopping sequences. Data is transmitted by generating a secondpulse signal in a next subband of the frequency hopping sequences. Thedata to be transmitted is determined according to the generated pulsestream, wherein the pulse stream is generated by a UWB sender (notshown).

FIG. 4 illustrates another distribution of a frequency band in aconventional UWB wireless communication system.

Referring to FIG. 4, 15 frequency subbands with 520 MHz bandwidths areallocated for a UWB frequency band. Except one frequency subbandcorresponding to a 5 GHz wireless LAN frequency band defined in the IEEE802.11a standard, 14 frequency subbands are used. The 14 frequencysubbands are divided into a low frequency group and a high frequencygroup, each group having 7 frequency subbands.

FIG. 5 illustrates frequency hopping sequences used for the distributionof the frequency band in FIG. 4.

The sequences include 6 frequency hopping sequences. A pulse isgenerated during a dwell time such that a 7 subband sequence is notduplicated among the 6 frequency hopping sequences, thus allowing 6piconets to use the 6 frequency hopping sequences. Data is transmittedby generating a second pulse signal in a next subband of the frequencyhopping sequences.

In both of the embodiments, 6 frequency hopping sequences are designedso that frequency subbands are not duplicated. First frequency subbandsof the 6 frequency hopping sequences are all the same because the firstfrequency subband is used as a reference frequency subband to easilysearch existing frequency hopping sequences when a new piconet isgenerated.

In a multi-user handling method in which one frequency hopping sequenceis used simultaneously by a plurality of piconets in a multi-band UWBsystem suggested as a standard for a physical layer of a WPAN, eventhough the frequency hopping sequence is designed such that frequencysubbands can be used flexibly according to a data transmission capacityof a single piconet by dividing the frequency subbands into a lowfrequency group and a high frequency group, the method cannot supportmore than 6 piconets. Furthermore, since subbands of the high frequencygroup are not used in a piconet in which a low data transmission rate isrequired, frequency usage efficiency is low.

Most multi-band UWB systems support a multi-piconet using frequencyhopping sequences using the frequency hopping sequence algorithmdescribed above. However, since the algorithm supports a maximum of 6piconets at any given time and does not use subbands of a high frequencygroup in a piconet in which a low data transmission rate is required, awaste of frequencies occurs.

SUMMARY OF THE INVENTION

The present invention provides a method of allocating frequency subbandscapable of efficiently using frequency subbands of a high frequencygroup and an apparatus adopting the same.

According to an aspect of the present invention, there is provided amethod of allocating frequency subbands to a device in a communicationsystem, the method comprising: (a) determining whether usage of a firstfrequency band including upper frequency subbands is necessary; and (b)if it is determined that the usage of the first frequency band isnecessary, not setting usage permission for the first frequency band tothe device and not granting access to the first frequency band althougha request for usage of the first frequency band is received from thedevice.

It is preferable that step (b) further comprises: if it is determinedthat the usage of the first frequency band is unnecessary, grantingaccess to the first frequency band when a request for usage of the firstfrequency band is received from the device.

It is preferable that the communication system uses an ultrawideband.

According to an aspect of the present invention, there is provided amethod of requesting frequency subband allocation in a communicationsystem which uses frequency subbands at predetermined intervals, themethod comprising: (a) scanning subbands of a second frequency bandincluding lower frequency subbands and determining whether all of thelower frequency subbands are used; (b) if it is determined that all ofthe lower frequency subbands are used, joining a piconet as a memberdevice; (c) requesting a subband of a first frequency band includingupper frequency subbands; and (d) receiving a grant signal.

It is preferable that the communication system uses an ultrawideband.

According to another aspect of the present invention, there is providedan apparatus that manages frequency subband allocation in acommunication system which uses frequency subbands at predeterminedintervals, the apparatus comprising: a determining unit, whichdetermines whether usage of a first frequency band including upperfrequency subbands is necessary; and a negotiator, which, if it isdetermined that the usage of the first frequency band is necessary, doesnot set usage permission for the first frequency band to the device orgrant access to the first frequency band if a request for usage of thefirst frequency band is received from the device.

It is preferable that the apparatus further comprises a scanner, whichscans subbands of a second frequency band including lower frequencysubbands.

It is preferable that the communication system uses an ultrawideband.

According to another aspect of the present invention, there is provideda computer readable medium having recorded thereon a computer readableprogram for performing the method.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 illustrates a network topology according to the IEEE 802.15.3standard;

FIG. 2 illustrates a distribution of a frequency band in a conventionalUWB wireless communication system;

FIG. 3 illustrates frequency hopping sequences used for the distributionof the frequency band of FIG. 2;

FIG. 4 illustrates another distribution of a frequency band in aconventional UWB wireless communication system;

FIG. 5 illustrates frequency hopping sequences used for the distributionof the frequency band in FIG. 4;

FIG. 6 illustrates a frequency hopping sequence of a low frequency groupand a high frequency group according to an embodiment of the presentinvention;

FIG. 7A is a flowchart illustrating an operation of a parent piconetPNC;

FIG. 7B is a flowchart illustrating an operation of a new piconet PNC;

FIG. 8A illustrates a protocol between a parent piconet PNC (or aprimary piconet PNC) and a new piconet PNC;

FIG. 8B illustrates a protocol between a primary piconet device and anew piconet PNC of a new piconet; and

FIG. 9 is a block diagram of a frequency band allocation managementapparatus.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, with reference to the accompanying drawings, an exemplaryembodiment of the present invention will now be described.

FIG. 6 illustrates a frequency hopping sequence of a low frequency groupand a high frequency group according to an embodiment of the presentinvention.

Referring to FIG. 6, 6 piconets simultaneously use 6 hopping patternsrespectively allocated thereto. A first piconet simultaneously uses thesame frequency hopping sequences in a low frequency group and a highfrequency group thus transmitting more data than a piconet using onlythe low frequency group. However, the other piconets can sufficientlytransmit data only in the low frequency group, and therefore transmitdata using only frequency subbands of the low frequency group withoutusing frequency subbands of high frequency group.

Since the frequency subbands of the low frequency group are allocated to6 different piconets, no other piconets can be generated. Furthermore,since the piconets other than the first piconet do not use subbands ofthe high frequency group, a waste of frequencies occurs.

If a potential new piconet PNC senses that 6 hopping sequences arealready used while seeking for a frequency subband by scanning 14subbands, the potential new piconet PNC cannot be formed. However, sincethe piconets other than the first piconet use only the frequencysubbands of the low frequency group, the frequency subbands of the highfrequency group are free.

In the above-described situation, the frequency subbands of the highfrequency groups can be used as follows.

First, a potential new piconet PNC can make the new piconet in a networkby making a child piconet of an established piconet through negotiationwith a PNC of the established piconet, which is not using a subband of ahigh frequency group, and using a hopping sequence of the establishedpiconet. If a transmission rate higher than that of a network of aparent piconet is necessary, the child piconet PNC can transmit datausing frequency hopping sequences of the low frequency group in subbandsof the high frequency group in addition to the low frequency group.

Second, if a potential new piconet PNC cannot make a new piconet becauseall hopping sequences are being used when the potential new piconet PNCis seeking a frequency hopping sequence, the potential new piconet PNCobtains a usage right of a subband of a high frequency group through anegotiation with a PNC of a piconet which is not using the subband ofthe high frequency group.

Referring to FIGS. 7A and 7B, a frequency subband allocation methodaccording to an embodiment of the present invention will now bedescribed in detail.

FIG. 7A is a flowchart illustrating operation of a parent piconet PNC.

When a parent piconet PNC is using subbands of a low frequency group instep S702, the parent piconet PNC determines whether a usage of subbandsof a high frequency group is necessary in step S704. If the usage of thesubbands of the high frequency group is unnecessary, a low frequencygroup usage mode is set in step S706, and if request for usage of asubband of the high frequency group is received from a device in stepS708, the parent piconet PNC grants access to the high frequency band instep S710.

If the usage of the subbands of the high frequency group is determinedto be necessary in step S704, usage of the subbands of the highfrequency group is not permitted in step S712, and even if a request forusage of a subband of the high frequency group is received from a devicein step S714, the parent piconet PNC does not grant access to the highfrequency band in step S716.

FIG. 7B is a flowchart illustrating operation of a potential new piconetPNC.

A potential new piconet PNC intending to make a new piconet scanssubbands of a low frequency group in step S750. The new piconet PNCdetermines whether all subbands of the low frequency group are beingused in step S752. If a free subband of the low frequency range does notexist, the potential new piconet PNC becomes a member of a child piconetof an established piconet in step S754, and negotiates allocation of asubband of a high frequency group with the established piconet in stepS756. That is, the potential new piconet PNC requests a right of usageof the subband of the high frequency group to a parent piconet PNC instep S758, and if the potential new piconet PNC receives a grant signalin step S760, the new piconet PNC performs communication in the subbandof the high frequency group in step S762.

If it is determined that a free subband of the low frequency group doesexist in step S752, the potential new piconet PNC determines whether togenerate a new frequency hopping pattern or become a member of a currentpiconet, and performs communication in the determined frequency subbandin step S764.

FIG. 8A illustrates a protocol between a parent piconet PNC (or aprimary piconet PNC) and a potential new piconet PNC.

Referring to FIG. 8A, when a primary piconet PNC transmits a beaconsignal to a potential new piconet PNC, the potential new piconet PNCbecomes a member of the primary piconet through association request andassociation response procedures in response to the beacon signal. Afterjoining, the potential new piconet PNC transmits a high frequency grouprequest signal and receives a grant signal. Then, the new piconet isformed.

FIG. 8B illustrates a protocol between a primary piconet device and anew piconet PNC of a new piconet in a high frequency band.

When the new piconet PNC transmits a beacon signal to the primarypiconet device during an operation, if the primary piconet device wantsto become a member of the new piconet in a high frequency group, theprimary piconet device becomes a member of the new piconet throughassociation request and association response procedures.

FIG. 9 is a block diagram of a frequency band allocation managementapparatus.

Referring to FIG. 9, frequency band allocation management is performedin a media access controller (MAC) layer management entity 900. The MAClayer management entity 900 includes a determining unit 910, a scanner920, and a negotiator 930.

The determining unit 910 determines whether usage of a first frequencyband including upper frequency subbands is necessary.

If it is determined that the usage of the first frequency band isnecessary, the negotiator 930 does not set usage permission for thefirst frequency band or grant access to the first frequency band even ifa request for usage of the first frequency band is received.

The scanner 920 scans subbands of a second frequency band includinglower frequency subbands.

A PNC and a device include the MAC layer management entity 900, atransmitter 940, and a receiver 950.

The present invention may be embodied in a general-purpose computer byrunning a program from a computer readable medium, including but notlimited to storage media such as magnetic storage media (ROMs, RAMs,floppy disks, magnetic tapes, etc.), optically readable media (CD-ROMs,DVDs, etc.), and carrier waves (transmission over the internet). Thepresent invention may be embodied as a computer readable medium having acomputer readable program code unit embodied therein for causing anumber of computer systems connected via a network to effect distributedprocessing. And the functional programs, codes and code segments forembodying the present invention may be easily deducted by programmers inthe art which the present invention belongs to.

As described above, when generation of a new piconet is necessary orgeneration of a new piconet is requested in a multi-piconet environment,since subbands of a high frequency group are allocated throughnegotiation, frequency resources are efficiently managed.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1-3. (canceled)
 4. A method of requesting frequency subband allocationin a communication system which uses frequency subbands at predeterminedintervals, the method comprising: (a) scanning subbands of a secondfrequency band including lower frequency subbands and determiningwhether all of the lower frequency subbands are used; (b) if it isdetermined that all of the lower frequency subbands are used by a seconddevice, a first device of the communication system joins a piconet as amember; (c) requesting a subband of a first frequency band includingupper frequency subbands; and (d) receiving a grant signal.
 5. Themethod of claim 4, wherein the communication system uses anultrawideband. 6-9. (canceled)
 10. The method of claim 4, wherein thefirst device of the communication system joins the piconet as a memberbecause a subband of a first frequency band including upper frequencysubbands are free.